Light-sensitive photographic paper



United ates Patent LIGHT-SENSITIVE PHOTOGRAPHIC PAPER Albert Emiel Van Hoof, Antwerp-Berchem, Belgium,

assignor to Gevaert Photo-Producten N.V., Mortsel- Antwerp, Belgium, a Belgian company No Drawing. Filed June 18, 1957, Ser. No. 666,475

Claims priority, application Belgium June 22, 1956 4 Claims. (Cl. 96--85) The present invention relates to the manufacture of improved photographic paper.

Crude photographic paper possesses a relatively uneven surface. Such paper coated with a light-sensitive emulsion is one on which photographic images can be ob-' tained. These images show a rather crude surface and no high-gloss can be obtained thereon.

It is already known in photographic techniques to coat this paper with a pigment-containing layer. Thus it is generally known to use therefor a finely divided barium sulphate in gelatin as binding agent. If such baryta-coated paper is coated with a photographic emulsion and dried, the images finished on this paper show a much higher gloss than those made on the above-mentioned crude paper without pigment-containing layer.

In order to obtain a still more glossing effect, the baryta coated paper is subjected, before applying the emulsion, to a so-called satinizing (whilst heating, the moistened baryta coated paper is rolled between smooth presses). By satinizing, the baryta-coated paper becomes more glossy indeed. This method, however, has the disadvantage that on moistening with water and drying, the gloss obtained by satinizing partly disappears again. In the circumstances, it is evident that the increased glossy effect of this satinizing only partly appears to its full advantage on the photographic images obtained on such baryta-coated and satinized paper: the moistening by applying the light-sensitive layer as well as the processing in the different photographic treating baths reduce the final gloss of the finished images.

It is an object of the present invention to obtain a high gloss in photographic papers. Another object is to obtain a high gloss on photographic paper which can still be attained after moistening the paper. Further objects will appear from the following description.

Now I have found that a very high gloss can be obtained on finished photographic images by applying a colloidal silicon dioxide layer to the baryta'coated paper. The images obtained according to the present invention show a much higher gloss than those obtained on baryta-coated and satinized paper. With an amount of baryta considerably smaller than that normally used for photographic paper combined with silicon dioxide a higher gloss is obtained than with the normal quantity of baryta without silicon dioxide. The gloss obtained with colloidal silicon dioxide moreover offers the advantage that it does not diminish by moistening (e.g. by applying the photographic emulsion or by treatment in the photo graphic baths). A further advantage is that even on grained papers a high gloss is obtained without disappearance of the grain structure.

The application of the silicon dioxide layer can be carried out by means of the known machines such as e.g. a baryta machine, an airknife etc.

The following factors play their role for regulating the strength of the gloss.

The glossing is higher according to Whether the silicon dioxide layer is applied to a smoother support. A baryta- 2,973,262 Patented Feb. 28, 1961 coated paper covered with thecolloidal silicon dioxide suspension glosses more strongly than crude paper pro vided with this same layer. Satinizing the silicon dioxide layer considerably strengthens the gloss and this increase of gloss is not lost on later moistening.

The gloss increases according to whether there is more silicon dioxide applied per surface unit (although not limited thereto, the quantities preferably vary between 1 and 20 g. per square meter).

According to the present invention the colloidal silicon dioxide suspension as available on the market can occasionally be applied for coating after dilution. It is advisable to add a water-soluble product which as plasticizer inhibits the appearance of fine cracks in the layer particularly when the latter is a thick one. The silicon dioxide suspension can also be mixed with a hydrophilic colloid such as gelatin.

The following examples illustrate the present invention without limiting, however, the scope thereof.

Example 1 A baryta-coated paper of g./m. is covered by means of an airknife with a layer of the following composition:

Cmfi Colloidal silicon dioxide suspension 1000 Glycerine 25 and, after satinizing, with a silver chloride emulsion. On exposure, development, fixation and washing, images are obtained which possess a stronger high-gloss than those obtained with ordinary satinized baryta-coated paper.

Example 2 A grained baryta-coated cardboard of 250 g./m. is covered with the following layer:

Cm. Colloidal silicon dioxide suspension 1000 Ethylene glycol 10 and next with a silver chloro-bromide emulsion. The

finished images obtained with this material are strongly glossing.

Example 3 A baryta-coated paper of 135 g./m. is covered by means of a baryta-coating machine with a layer of the following composition:

10% (weight/volume) gelatin 5000 Colloidal silicon dioxide suspension containing 30% dry substance 1650 Ammonium hydroxide 6 N 10 and, after satinizing, with a silver chloride emulsion. The finished images obtained with this material are strongly glossing.

I claim:

1. High gloss photographic light-sensitive paper comprising a paper support, a baryta coating on said sup-' coating, the silica coated paper having a higher glossv than a similarly coated paper without a silica coating, the final gloss being undiminished by moistening.

3 i 2. High gloss photographic light-sensitive paper ac- References Cited in the file of this patent cording to claim 1, in which the additive in the silica UNITED STATES PATENTS layer glycerme' 290,655 Wright Dec. 18, 1883 3. High gloss photographic light-sensitive paper according to claim 1, in which the additive in the silica layer 5 382369 Mayan May 1888 is hy glycol. 2,433,515 Iahoda Dec. 30, 1947 4, Hi h gloss photographic light-sensitive paper 210- %g 3 Wqbsger 1953 cording to claim 1, in which the additive in the SiliCfl g ens 1954 layer i gelatin, and said additive further contains am- 25 an 1956 monium hydroxide 10 2,789,054 Land Apr. 16, 1957 

1. HIGH GLOSS PHOTOGRAPHIC LIGHT-SENSITIVE PAPER COMPRISING A PAPER SUPPORT, A BARYTA COATING ON SAID SUPPORT, A SEPARATE COATING COMPRISING ESSENTIALLY COLLOIDAL SILICA, AN ADDITIVE SELECTED FROM THE GROUP CONSISTING OF WATER-SOLUBLE PLASTICIZERS AND GELATIN, SAID ADDITIVE NOT EXCEEDING THE AMOUNT OF SAID SILICA, SUPERPOSED DIRECTLY ON SAID BARYTA COATING, AND A SEPARATE LIGHT-SENSITIVE SILVER HALIDE EMULSION COATING SUPERPOSED DIRECTLY ON SAID SILICA COATING, THE SILICA COATED PAPER HAVING A HIGHER GLOSS THAN A SIMILARLY COATED PAPER WITHOUT A SILICA COATING, THE FINAL GLOSS BEING UNDIMINISHED BY MOISTENING. 